Functional Consequences of Various Leucine Mutations in the M3/M4 Loop of the Na+,K+-ATPase α-Subunit

Functional Consequences of Various Leucine Mutations in the M3/M4 Loop of the Na+,K+-ATPase... Leucines were mutated within the sequence L311ILGYTWLE319 of the extracellular loop flanking the third (M3) and fourth (M4) transmembrane segments (M3/M4 loop) of the Torpedo Na+,K+-ATPase α-subunit. Replacement of Leu311 with Glu resulted in a considerable loss of Na+,K+-ATPase activity. Replacement of Leu313 with Glu shifted the equilibrium of E1P and E2P toward E1P and reduced the rate of the E1P to E2P transition. The reduction of the transition rate and stronger inhibition of Na+,K+-ATPase activity by Na+ at higher concentrations together suggest that there is interference of Na+ release on the extracellular side in the Leu313 mutant. Thus, Leu313 could be in the pathway of Na+ exit. Replacement of Leu318 with Glu yielded an enzyme with significantly reduced apparent affinity for both vanadate and K+, with an equilibrium shifted toward E2P and no alteration in the transition rate. The reduced vanadate affinity is due to the lower rate of production of vanadate-reactive [K+ 2]E2 caused by inhibition of dephosphorylation through reduction of the K+ affinity of E2P. Thus, Leu318 may be a critical position in guiding external K+ to its binding site. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Functional Consequences of Various Leucine Mutations in the M3/M4 Loop of the Na+,K+-ATPase α-Subunit

Loading next page...
 
/lp/springer_journal/functional-consequences-of-various-leucine-mutations-in-the-m3-m4-loop-zK0f0895VI
Publisher
Springer-Verlag
Copyright
Copyright © 2008 by Springer Science+Business Media, LLC
Subject
Life Sciences; Human Physiology ; Biochemistry, general
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s00232-007-9091-3
Publisher site
See Article on Publisher Site

Abstract

Leucines were mutated within the sequence L311ILGYTWLE319 of the extracellular loop flanking the third (M3) and fourth (M4) transmembrane segments (M3/M4 loop) of the Torpedo Na+,K+-ATPase α-subunit. Replacement of Leu311 with Glu resulted in a considerable loss of Na+,K+-ATPase activity. Replacement of Leu313 with Glu shifted the equilibrium of E1P and E2P toward E1P and reduced the rate of the E1P to E2P transition. The reduction of the transition rate and stronger inhibition of Na+,K+-ATPase activity by Na+ at higher concentrations together suggest that there is interference of Na+ release on the extracellular side in the Leu313 mutant. Thus, Leu313 could be in the pathway of Na+ exit. Replacement of Leu318 with Glu yielded an enzyme with significantly reduced apparent affinity for both vanadate and K+, with an equilibrium shifted toward E2P and no alteration in the transition rate. The reduced vanadate affinity is due to the lower rate of production of vanadate-reactive [K+ 2]E2 caused by inhibition of dephosphorylation through reduction of the K+ affinity of E2P. Thus, Leu318 may be a critical position in guiding external K+ to its binding site.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Jan 23, 2008

References

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 12 million articles from more than
10,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Unlimited reading

Read as many articles as you need. Full articles with original layout, charts and figures. Read online, from anywhere.

Stay up to date

Keep up with your field with Personalized Recommendations and Follow Journals to get automatic updates.

Organize your research

It’s easy to organize your research with our built-in tools.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve Freelancer

DeepDyve Pro

Price
FREE
$49/month

$360/year
Save searches from Google Scholar, PubMed
Create lists to organize your research
Export lists, citations
Access to DeepDyve database
Abstract access only
Unlimited access to over
18 million full-text articles
Print
20 pages/month
PDF Discount
20% off